Processes for conveying a particulate solid fuel from an atmospheric container by means of a lock system to a reactor in which the fuel is partially combusted at elevated pressure to synthesis gas are known. Generally, the fuel is conveyed from the container to a lock hopper that is pressurized by pressing an inert gas into the lock hopper and then the fuel is subsequently passed from the lock hopper to a pressure vessel at at least the same pressure as that in the reactor and from the pressure vessel to the reactor.
The process is used in the gasification of solid fuel. The fuel reacts with the oxygen-containing gas owing to which the synthesis gas is formed, a gas mixture mainly consisting of carbon monoxide and hydrogen. In addition to an oxygen-containing gas, a moderator is preferably introduced into the reactor for the conversion of the fuel. A moderator has a moderating effect on the temperature of the partial combustion, since it reacts endothermically with the products and/or reactants of the partial combustion reaction. Suitable moderators are steam and carbon dioxide.
As suitable fuel coal and brown coal, oil shale, wood etc., are considered.
As oxygen-containing gas air can be used. The resulting synthesis gas, however, then contains a considerable quantity of nitrogen. To prevent this oxygen-enriched gas or substantially pure oxygen is usually applied. The oxygen is generally obtained from an apparatus in which air is separated into oxygen and nitrogen.
The pressure in the reactor is preferably 15-80 bar.
The resulting synthesis gas can be used for a variety of purposes. It can be used as fuel. Its hydrogen content can be increased by converting carbon monoxide with steam into carbon dioxide and hydrogen. After its separation from the resulting gas mixture the hydrogen can be used in the synthesis of ammonia. The synthesis gas can also serve as raw material for the synthesis of hydrocarbons and/or oxygen-containing hydrocarbons, such as methanol. In that case pure oxygen is preferably used as oxygen-containing gas in the partial combustion.
Before the fuel is introduced into the reactor by means of the lock system, the fuel is preferably ground and dried. By the grinding fine fuel particles are obtained, which contributes to a good gasification. The water present in the fuel is vaporized in the reactor. The vaporization requires energy, which may adversely affect the gasification. To avoid this the fuel is dried. Moreover, the low water content facilitates the transport of the fuel with a carrier gas, since the fuel particles are now less inclined to stick together.
Nevertheless, dried particles can sometimes also stick together when they lie packed in the lock system. Then bridging may occur across the discharge of a vessel to another vessel. Consequently, the transport of the particles is impeded. The present invention aims at providing a process in which the fuel particles no longer stick together. Another object of the invention is to provide a process in which the fuel is passed to the reactor in a carrier gas, without the synthesis gas to be formed being contaminated by gaseous components in the carrier gas.